GEOGRAPHICA
NATURE
ACreature With 50,000 "Eyes"
Brittle star's tiny lenses may spur optical technology
None of the echinoderms,
such as sea stars and
brittle stars, appear to
have eyes. But marine biologists
diving on reefs have noticed that
some brittle stars seem to see
them coming and flee. They also
sport a darker hue during day
light and turn lighter at night.
"So we wondered just what
was going on," says Joanna
Aizenberg, a materials scientist
at Lucent Technologies' Bell
Laboratories. She has made an
astonishing discovery: At least
one brittle star species, Ophio
coma wendtii, is covered with
50,000 to 100,000 tiny lenses that
gather light like eyes.
"By day it's as if they're wear
ing sunglasses,"
she says. "They
exude pigment
that covers the
lenses and
blocks light
(left, top)." At
night, bottom,
the brittle star
uncovers the
lenses, made
of calcite crystals. They appear
as bumps in the close-up, above.
Aizenberg says the lens array
may help scientists improve
technology such as fiber optics.
CONSERVATION
Last Stand for Ibis?
long the Moroccan coast,
a handful of large birds
with curved bills cling to
the sea cliffs where they breed.
Once widespread in Europe, the
Middle East, and North Africa,
the northern bald ibis has dwin
dled to about 300 individuals,
partly due to habitat loss. In
1991 the Moroccan government
created Souss-Massa National
Park as a refuge for the ibises,
and seven local people have been
trained as wardens to protect
them. But some of the parkland
to BirdLife International. The
was reserved for tourism devel-
group is working with Club Med
opment-land that is critical
to ensure that a planned resort
to the ibises' survival, according
will also accommodate the ibises.
NATIONAL GEOGRAPHIC * SEPTEMBER 2002